I. Field of the Invention
This invention relates to a submersible pump construction and, in particular, to a multi-stage submersible pump with a variable length plastic housing to vary the number of stages and a method of manufacturing the housing.
II. Description of the Prior Art
Multi-stage submersible pumps are widely known and utilized in both commercial and residential applications. Such pumps use multiple pumping stages mounted to a rotating shaft to pump the fluid from one end of the pump to the other. The pumping requirements determine the number of stages in the pump and as a result pump housings of different lengths must be utilized for the different size pumps to accommodate the stages. In past known pump constructions, the housing includes an inlet head which is attached to the drive motor, a discharge head and a casing sleeve normally constructed of stainless steel. By varying the length of the casing sleeve a different number of stages can be accommodated to increase pump performance. The cartridge assembly consisting of the individual pumping stages is compressed between the inlet and discharge heads to control leakage between the stages. Although reducing the costs associated with the manufacture of multi-stage pumps, such constructions can have significant weight associated therewith since normally the inlet head and discharge head are made of cast iron or brass.
In an attempt to reduce the weight of the pump as well as manufacturing costs, plastic components have been substituted in past known pumps. Plastic impellers and diffusers are utilized to provide the multiple stages of the pump. Such impellers and diffusers are in the form of stages which stack on the shaft whereby they are forceably engaged to control fluid leakage between the stages which results in better pump performance and efficiency as a result of lower fluid pressure on the interior of the housing. Attempts to provide a plastic housing have not met with total success either because of fluid leakage or the limited number of stages which may be incorporated. Past known plastic housing pumps have molded the diffuser plate into the housing while segregating the pump stages which results in leakage between the housing halves and decreased pump efficiency as a result of the fluid loss.
The one advantage that the stainless steel sleeve housings had over the past known plastic housings is the capability of accommodating a wide range of impeller stages simply by manufacturing sleeves of different lengths. In contrast, a different mold had to be made for the different sized plastic housings resulting in increased inventory and manufacturing costs.